Mengovirus (variant 2T) was shown for the first time to infect pancreatic beta cells and produce abnormal glucose tolerance tests in mice. The spectrum of host susceptibility to Mengovirus-induced diabetes was found to be quite different from that of encephalomyocarditis (EMC) virus-induced diabetes. Studies on the genetics of susceptibility to EMC-induced diabetes were carried out in New Zealand mice. Androgens appear to play an important role in the development of this disease, at least in the F1 generation. Reovirus-induced autoimmune polyendocrine disease was studied in greater depth. Earlier studies showed that this disease could be prevented by immunosuppression. Work this year on helper and suppressor cells suggest that the viral infection may influence the host's immunoregulatory system.